Waterborne Disease Outbreaks and the Multi-barrier Approach to Protecting Drinking Water - Global Drinking Water Management and Conservation - page 23

continues past the Walkerton outbreak to pose the highest risk to water systems. With
the extent of research and the numerous outbreaks associated with this dominant
pathogen, it is surprising that outbreaks continue to occur.
The Hrudeys also emphasize the effects of a change on a drinking water system.
A system that is adaptable to change will be more capable of providing safe
drinking water. Change can include changes in the weather, changes within the
community, and changes within the water system. This is a contributing factor in
many of the mentioned outbreaks. Change in the weather, either due to season
changes or severe rainfalls associated with climate change, prior to the occurrence
of outbreaks is a common event, such as in the outbreak of Carrollton Georgia in
1987, Warrington England in 1992, Cranbrook B.C. in 1996, and Galway Ireland
in 2007. Change in a community can occur from human activity, such as farming.
Agricultural runoff from farming activity was the speci

ed cause in outbreaks such
as Jackson County Oregon in 1992, Warrington England in 1992, and in Galway
Ireland in 2007. Change in a water system contributed to outbreaks such as
Kitchener in 1993 when the water system switched from a groundwater source to a
surface source, and also in Pitts filtration plant

was in the process of being installed. Change should act as a warning to system
operators of possible contamination. Monitoring should be heightened during times
of change, and precautions may be necessary.
The conclusions by Hrudey and Hrudey ( 2004 ), based on outbreaks prior to
2002, emphasize that the Walkerton outbreak should have served as a major
landmark in the history of contaminations. However, it does not seem that water
authorities have absorbed lessons from that outbreak, as outbreaks have continued
to occur since then. The conclusions and lessons described by the Hrudeys in their
book can therefore be further expanded with new information by including out-
breaks after 2002. The outbreak in Gwynedd and Anglesey, Wales in 2005 and the
outbreak in Galway Ireland in 2007 are the most recent outbreaks. Including these
cases provides the opportunity to consider whether outbreaks have changed patterns
after Walkerton. Considering the patterns among the outbreaks is important in
determining what factors contribute to the occurrence of an outbreak.
From the analysis of outbreaks reported here, we can conclude that there are no
seasonal patterns to outbreaks. Contaminations have continued to occur during
spring runoff from winter thaws and with higher amounts of rainfall. However,
outbreaks can occur at any time during the year. This can be observed from the
outbreaks reported here, as over half of the outbreaks surveyed here did not occur in
the spring season. Spring runoff and rainfall are natural events, but improper
practices by system operators can also cause outbreaks. Frequent human failures
that cause outbreaks include improper and ineffective treatment, insuf

eld Massachusetts in 1985 when a

cient mon-

itoring, and inadequate training of operators.
We can also conclude that outbreaks do not follow a pattern based on the size of
a water system. In contrast to what may be a common belief, outbreaks are not
speci c to only small rural areas. Although outbreaks may be more frequent in

smaller towns because of lower maintenance and less ef

cient water systems, due to

lack of finance, this does not mean that larger systems are immune from failure.